In wireless networks care is given to the scheduling of transmissions both in the time and frequency domain from user equipments (UEs) to base stations. If the UEs are located close together spatially and there is a significant overlap in the time and frequency at which uplink transmissions from the UEs are sent to a base station, there will be interference between the UEs' transmissions. This interference may mean that the quantity of information per transmission burst from each UE which can be successfully decoded is small (i.e. they may need to choose a low-order modulation alphabet).
Conventionally, to overcome this deficiency, networks assign each UE transmitting to a base station a different time-frequency resource block in which to transmit. Since the UEs within a cell now do not interfere with one another, they can each transmit more information per transmission burst (e.g. by choosing a higher-order modulation alphabet)
However, the assignment of separate (non-shared) time-frequency resource blocks limits the resource allocated to a UE's transmission burst, since the overall resource on the wireless medium is generally shared equitably between the users.
One technique that is used to make more efficient use of the available resource involves co-scheduling pairs of UEs on the same time-frequency resource block. In this technique UEs are only co-scheduled when the signals from the UEs are deemed to be sufficiently segregated spatially. However, when co-scheduling is implemented in this manner residual interference may still occur at the receiver, for example due to any remaining overlap between the UE signals, reducing the quantity of information per transmission burst from each UE which can be successfully decoded. The invention described herein relates to techniques for optimally selecting UEs for co-transmission such that any remaining residual interference is minimised.